The present invention is directed to a relief pattern on a substrate. More particularly, the present invention relates to a substrate having a seamless surface relief embossed or cast therein and a sleeve and method for making same.
Pressing a surface relief into a substrate under heat and pressure results in a “transfer” or replication of the surface relief onto the substrate. A surface relief is a structure, image, or representation of a three-dimensional (3D) relief, holographic image, diffractive pattern, non-diffractive pattern, or surface texture. A substrate is a material that can receive a surface relief, such as a continuous web of film(s), foil(s), coated film(s), coated foil(s), or coated paper or board, that may be untreated or pre-treated, as by plasma, metalizing, vacuum coating or the like, as desired. A metal or plastic shim (hereafter “shim”) is often used to transfer the surface relief onto the substrate.
Typically, a shim is created as a flat sheet that is then wrapped around and attached (mounted) to a large cylindrical roller (hereafter “cylindrical base”) using adhesives and/or fasteners. The cylindrical base, with the shim mounted thereon, is mounted into an embossing or casting assembly wherein an impression or replication of the surface relief is transferred from the shim onto the substrate during the embossing or casting process.
The resulting embossed or cast substrate is generally accumulated on large rolls which can be cut into smaller rolls or sheets as desired for a variety of uses such as wallpaper, wrapping paper, magazines, and the like. The roll or sheets of embossed or cast substrate also can be printed, metalized and/or laminated to board stock, plastic films, or other surfaces to create decorative, secure, and/or functional surfaces that have distinctive images, patterns, textures or color variations as the viewing angle changes.
While using shims on cylindrical bases is an effective method in producing embossed or cast substrates, there are several disadvantages to using shims. First, shims are time-consuming to prepare. Several steps, including creating an image onto a photoresist plate, plating, coating, peeling, and the like are only a few of the steps involved in producing one shim.
In addition, wrapping a flat shim around a cylindrical base leaves a void or join line where the side edges of the shim meet. Furthermore, in some cases, the cylindrical base may be of such length that one shim is insufficient to cover the entire length of the cylindrical base. Accordingly, there may be more than one flat shim required to cover the surface of the cylindrical base. When more than one shim is present, not only is a join line present where the ends of the shim meet when encircling the cylindrical base, but there are also join lines evident where the two or more shims abut one another along the width of the cylindrical base. Consequentially, with each revolution of the cylindrical base, an impression of the join line(s) is transferred into the substrate along with the surface relief. These join lines are often referred to as a repeats, interruptions, or seams (hereafter collectively referred to as “seam(s)”) that are visible on the substrate. With multiple shims per cylindrical base, there can be an increasing number of seams. The multiple seams create a “parquet” effect on the embossed or cast substrate, not unlike multiple tiles on a floor.
Seams present in the final embossed or cast substrate are difficult to eliminate in the final product. Seams can be particularly noticeable in continuous holographic or textured patterns and are highly undesirable.
Therefore, in order to ensure that seams do not appear as flaws or defects in an end product, when cutting the embossed or cast substrate, downstream converters are forced to calibrate and register or index equipment to avoid incorporating the seams into the end product. Having to work around the seams increases the material scrap; a great deal of waste is produced in addition to the inconvenience of having to calibrate machinery to avoid the transition areas while cutting the embossed or cast substrate to size.
Furthermore, once the shims have been used in the embossing or casting processes, the shims are difficult to remove from the cylindrical base when the shim is no longer useful. The shim needs to be scraped off the cylindrical base in order for the cylindrical base to be prepared for a different shim. The used shim cannot be recovered or stored and is no longer useful as a shim. Once removed, the shim is then discarded as waste or recycled and the cylindrical base needs to scrubbed and prepared to host a new shim.
Efforts to reduce reliance on shims included forming the surface relief directly onto a photoresist material on the cylindrical base itself. Unfortunately, photoresist or other typical material used cannot withstand high temperature. Usually, the photoresist or other materials can only endure temperatures of less than 150 degrees Celsius; in addition, the embossing or casting cylinder and resultant embossed or cast substrate has less durability than perhaps is desired. Another method involved etching a surface relief directly onto the cylindrical base. In both cases, however, the cylindrical base cannot be reused for other patterns once the surface relief formed thereon is no longer useful. In addition, the size, weight, and cost of cylindrical bases makes forming the surface relief directly on the cylindrical base impractical.
Accordingly, there is a need for an embossed or cast substrate having no seams. Desirably, such an embossed or cast substrate is formed using an embossing media that is easy to manufacture, cost effective, easily removed, storable, and reusable, while minimizing necessary cleaning and maintenance of associated machinery.